Sooo, what’s the big deal?

During a train trip west, a friend and I entered the observation car to listen to a tour of Navajoland presented by a guide familiar with the area.

As unrepentant English teachers, we noticed instantly a speech mannerism of the fellow at the microphone: He ended every sentence with “so . . .” and the sentences would trail off, with nothing logically connected to the “so.”

“Why’s he doing that?” I asked Dick Panofsky, who was traveling with me to Flagstaff to visit a college communications department. We puzzled over the habit, which the speaker never failed to use, like this: “There are thousands of hogans hidden in the hills, so . . .” or “The Navajo tribe is the largest American Indian tribe, so . .

We thought about the pervasiveness of “so” and wondered what had happened in the language to make it the ender for every sentence. At Northern Arizona University, the next day, we discovered that “so” was not unique to tour guides. In fact, the college’s speech coach, who gave a 20-minute lecture on their program, sprinkled her presentation with “so” as well.

The world’s second-tiniest word once served as a shortcut for “therefore” for those who didn’t want to appear haughty. But putting either word at the end of a sentence somehow doesn’t seem grammatical. It stands out as much as “like,” which teenage girls, usually named Jennifer, inject into sentences.

This is what you’re likely to overhear: “He’s like ‘I want to see you again, so . . .’ and I’m like ‘Not in my lifetime.’ and he’s like ‘Why not?’ and I’m like ‘Cuz I said so.’”

The prevalence of “so” now prompts the question: Have people just begun this rhetorical habit, or has it been there all the time, but gone unnoticed?

Panofsky had a brilliant theory. He said that by tacking on “so” to sentences, we “reserve for ourselves the space to continue without being interrupted.”

So, if we say “so” at the end of the sentence, we warn others something else is coming, so don’t interrupt.

Often, we don’t even know what we’re saying next, and we hope to buy time by uttering the word. Fair enough, but our tour guide wasn’t likely to be interrupted, “so” or not. He was the one holding the mike.

I’d filed that sophisticated theory somewhere, only for it to be brought out of cold storage when John Martinez of Art and Stones showed me an article by a Washington Post writer, Linton Weeks, who calls “so” a word “that arguably packs the most sizzle for its size.”

Weeks refers to “so” as a common connector for our small global village. And “so” doesn’t always have to end a sentence; it can begin one as well. You bring it up to a stranger while in line at a commencement, and it’s as if you’d shared intimate secrets forever, as in “So, I imagine you have a son or daughter graduating; my son’s getting his degree and plans to move to Watrous or Baltimore, so …”

Before becoming aware of the terminal “so,” I’d discourage my students from using it as an intensifier, as in “He loves her so much.” “So much?” I’d generally ask, in the margin of the essay, “So much as what? So much that he can’t live without her? So much (or as much) as a million stars?” A former student I met years later brought up that useful marginal admonition, then said good-bye with, “Again, I thank you so much!”

Think of the many contexts in which “so” fits; it qualifies as several parts of speech:

“The desk is so wide,”

“He’s a repugnant so-and-so,”

“So what if I ate all the so-paipillas?”

“So that’s your game,”

“I like my soup cooked just so,”

“My mind is made up and will remain so,”

“Is that so?”

“Well, so long.”

Michael Lewis, author of “The New York Thing: A Silicon Valley Story,” says “so” “cuts across the borders within the computing class just as ‘like’ cuts across the borders within the class of adolescent girls.”

And another author says “so” is useful because it ends in a vowel, “which can be shortened or lengthened to fit all manner of emotional tones, settings and situations.”

Imagine lecturing and saving the most important point for the conclusion.

You want to make sure no eczematous teen interrupts you with, “Would you please reiterate and elaborate on that point?” So, you bring out the heavy armor: instead of merely ending the thought with “so . . .,” you make it “sooo . . . ,” to show the listeners you really mean it. So, no matter what, don’t interrupt.

There are some variations, including “soo,” (pronounced so-oh, not like zoo) and three “o’s” following the “s,” like this: “Sooo …?” “Soo” may be followed only by “not,” as in “You’re soo not nerdy.”

“Sooo” should not be tried at home and must be handled only by trained professionals or politicians. “Sooo” should come only when one’s faced with incontrovertible evidence of misdeeds, the political equivalent of getting a hand stuck in the cookie jar.

So, when a politician gets accused of granting a political favor that immediately follows the receipt of a hefty donation, the reaction — always followed by a question mark — has to be “Sooo? I admit appointing the donor to a sinecure-like position in government, but the appointment has nothing to do with the donation. So . . .”

The unspoken words following “sooo” are “What’s wrong with that? Everybody does it. So . . .”

And to that we say, “Sooo be it.”